National Electrical Code Explanations

Based on the 2020 NEC

by Mark Lamendola

National Electrical Code Tips: Article 760, Fire Alarm Systems, Part 3

  1. If your alarm circuit is a Non Power Limited Fire Alarm circuit (NPLFA), then unlike the Power Limited Fire Alarm circuit (NPLFA) it's basically a Chapter 3 wiring job [760.46]..
  2. You can run Class 1 and NPLFA in the same raceway [760.48(A)].
  3. You can run power supply and NPLFA circuit conductors in the same raceway too, but only if they connect to the same equipment [760.48(B)].


  4. You can't use aluminum conductors for fire alarm circuits [760.49(A)], and the conductors you do use must be rated at 600V or more [760.49(B)]. Alunimum conductors have a higher impedance than copper conductors (it's a function of the difference in the electron shells of aluminum versus copper) and run hotter. While the NEC permits aluminum conductors in many types of applications, it almost always is better to use copper.
  5. You determine the raceway fill per 300.17 [760.51(A) and (B)].
  6. Multiconductor NPLFA cables have so many requirements attached to them, the requirements take up 3/4 of a page [760.53]. Before considering such a wiring method, read this subsection carefully.



     

  7. The requirements for Power Limited Fire Alarm (PLFA) circuits take up nearly twice as much room in the NEC as those for NPLFA circuits. That isn't because the CMP just decided to be verbose or something. PLFA necessarily have tighter restrictions on the kinds of cables you can use and how you install them.
  8. A PLFA power source must be one of three things: Listed PFLA or Class 3 transformer, listged PLFA or class 3 power supply, or listed equipment marked to identify the PLFA source [760.121].
  9. The branch circuit supplying this equipment cannot supply other loads [760.121(B)]. Also, the OCPD for that circuit must have its location clearly indicated at the fire alarm control unit.
  10. Ensure any plainly visible equipment supplying PLFA circuits is durably marked to indicate each circuit that's a PLFA circuit [760.124].